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POMapReduce and grouping by date on MongoDb
 

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  1. POMapReduce and grouping by date on MongoDb
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    <p>I'm trying to test out mongoDb to manage our performance logs.</p> <p>For this test I inserted 10M rows in a collection using the following format</p> <pre><code>{ "_id" : ObjectId("4e9d3cc4621dc1dc11000000"), "date" : "Thu Oct 13 2011 15:37:21 GMT+0200 (CEST)", "loadtime" : 0.07, "msg" : "Lorem ipsum message" } </code></pre> <p>Now I would like to be able to get average load time by day.</p> <p>So from what I understood I need to do 2 pass of MapReduce.</p> <p>the first one would be to create a collection of days.</p> <p>So I tried </p> <pre><code>map = function() { day = Date.UTC(this.date.getFullYear(), this.date.getMonth(), this.date.getDate()); emit({day: day}, {count: 1}); } reduce = function(key, values) { var count = 0; values.forEach(function(v) { count += v['count']; }); return {count: count}; } </code></pre> <p>Refering to <a href="http://cookbook.mongodb.org/patterns/unique_items_map_reduce/" rel="nofollow">http://cookbook.mongodb.org/patterns/unique_items_map_reduce/</a></p> <p>But this kills my mongodb server after a few seconds.</p> <pre><code>db.loadTime.mapReduce(map, reduce, {out: 'days'}); Tue Oct 18 11:57:28 query failed : test.$cmd { mapreduce: "loadTime", map: function () { day = Date.UTC(this.date.getFullYear(), this.date.ge..., reduce: function (key, values) { var count = 0; values.forEach(functio..., out: "days" } to: 127.0.0.1 Tue Oct 18 11:57:28 Error: error doing query: failed (anon):1509 </code></pre> <p>Here is my error log</p> <pre><code>Tue Oct 18 11:56:08 [conn1] CMD: drop test.tmp.mr.mapreduce_1318931768_1_inc 55800/10000000 0% 112800/10000000 1% 171400/10000000 1% 229600/10000000 2% 288600/10000000 2% 345600/10000000 3% 404100/10000000 4% 462900/10000000 4% 522000/10000000 5% 579100/10000000 5% 629200/10000000 6% 677000/10000000 6% 724200/10000000 7% 767500/10000000 7% 818600/10000000 8% 864300/10000000 8% 921300/10000000 9% 972200/10000000 9% 1021600/10000000 10% 1070700/10000000 10% 1115600/10000000 11% 1163600/10000000 11% 1217400/10000000 12% 1269100/10000000 12% 1313300/10000000 13% 1366200/10000000 13% Tue Oct 18 11:57:28 Got signal: 11 (Segmentation fault). Tue Oct 18 11:57:28 Backtrace: 0x843a16d 0x842dbcd 0x741400 0x1eadcd /usr/lib/mongodb/mongod(_ZN5mongo15printStackTraceERSo+0x2d) [0x843a16d] /usr/lib/mongodb/mongod(_ZN5mongo10abruptQuitEi+0x3ed) [0x842dbcd] [0x741400] /usr/lib/xulrunner-2.0/libmozjs.so(+0xdadcd) [0x1eadcd] </code></pre> <p>Am I going in the right direction ?</p>
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